Nevadia is an extinct genus of redlichiid , with species of average size (about long). It lived during the Atdabanian stage, which lasted from 530 to 524 million years ago, in what are today Western Canada, the Western United States, and Mexico.
Etymology
Nevadia is named for the US State of Nevada, where the first specimens of this genus where found.
N. fritzi in named in honor of W.H. Fritz, a
Paleontology who worked on olenelloid trilobites.
Description
The body of
Nevadia is very flat dorso-ventrally. The general outline of its thin, lightly calcified
exoskeleton is inverted wide drop-shaped. The front is rounded, widest at the back of the headshield (or cephalon), and tapering from there to an eventually rounded termination. The central area of the cephalon (or glabella) is distinctly tapered forward, sides slightly concave, but not wedging out in the frontal half and with a narrow rounded front. The glabella and the frontal margin do not touch (in jargon: the preglabellar field is present). Cephalic margin clearly less wide as the most frontal thoracal segment. The thorax has 27 segments. The segments look a bit degenerated behind the 15th to 18th (or an opisthothorax can be distinguished). The pleural spines are long and sickle-shaped. The tailshield (or pygidium) is very small and subquadrate in shape.
Distribution
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Nevadia ovalis occurs in the Lower Cambrian of the Northwest Territories, Canada (Sekwi Formation, Mackenzie Mountains), and Mexico (Senora).
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Nevadia parvoconica and Nevadia sp., have been collected at the Mural Formation, Mumm Peak Section, Canada, .
[W. H. Fritz. 1992. "Walcott's Lower Cambrian Olenellid trilobite collection 61k, Mount Robson Area, Canadian Rocky Mountains". Geological Survey of Canada Bulletin 432. 1–66 [1]]
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Nevadia weeksi and Nevadia sp., were found at Cinnamon Peak-Whitehorn Mountain, Section, Mural Formation, Canada, ;
[J. S. Hollingsworth (1999). "A second candidate position for the base of the Montezuman". Laurentai 99: V field conference of the Cambrian Stage Subdivision Working Group, International Subcommission on Cambrian Stratigraphy 42–46.[2][3]]
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Nevadia weeksi occurs near the base of the Montenegro Member, Campeto Formation, Northeast of Barrel Spring, Nevada, USA, .
[W. H. Fritz (1995). " Esmeraldina rowei and associated Lower Cambrian trilobites (1f fauna) at the base of Walcott's Waucoban Series, southern Great Basin, U.S.A." Journal of Paleontology 69 (4): 708–723 [4]]
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Nevadia sp., was collected at Puerto Blanco, Unit 3, Cerro Rajon, Caborca Region, Mexico, ;
[J. Stewart, M. A. S. McMenamin, and J. M. Morales-Ramirez (1984). "Upper Proterozoic and Cambrian rocks in the Caborca Region, Sonora, Mexico - physical stratigraphy, biostratigraphy, paleocurrent studies, and regional relations". U. S. Geological Survey Professional Papers (1309)1–33.[5]] and at the Nevadella zone, Old Dominion Limestone Formation, Colville, Washington, USA, .[ J.J. Sepkoski Jr. 1998]
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Nevadia parvoconica, was found at the Middle Member of the Poleta Formation, Esmeralda County, Nevada, USA.
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Nevadia saupeae, was recovered from the Sekwi Formation, Mackenzie Mountains, Northwest Territories, Canada
Taxonomic
Nevadia predates
Nevadella and according to cladistic analysis includes its direct ancestor.
Species previously assigned to Nevadia
Habitat
Nevadia species were probably marine bottom dwellers, like all
Olenellina.
